There has been known an air conditioner that has an indoor evaporator and an indoor condenser arranged in a chamber and that cools and dehumidifies air to be blown into the chamber by the indoor evaporator and that reheats the air, which has been dehumidified by the indoor evaporator, by the indoor condenser and that blows off the air into the chamber to thereby dehumidify the interior of the chamber (see, for example, patent document 1 (JP-B1-3645324), patent document 2 (JP-6-341732A)).
In an air conditioner described in the patent document 1, a heating and dehumidifying operation of dehumidifying feed air at the time of heating the interior of the chamber and a moderate cooling and dehumidifying operation of dehumidifying feed air at the time of cooling the interior of the chamber can be performed by switching a refrigerant passage of a refrigerant cycle of a vapor compression type.
Specifically, at the time of performing the heating and dehumidifying operation, the refrigerant passage of the refrigerant cycle is switched to a refrigerant passage of coupling the indoor evaporator to an outdoor heat exchanger, which makes a refrigerant exchange heat with an outdoor air, in parallel on the downstream side of the indoor condenser to thereby make the outdoor heat exchanger function as a heat absorbing device. In this case, the refrigerant absorbs heat from the feed air in the indoor evaporator, and the refrigerant absorbs heat from the outdoor air in the outdoor heat exchanger, whereby an amount of heat radiated by the refrigerant in the indoor condenser can be ensured. In this way, the feed air having a high temperature can be blown off into the chamber.
On the other hand, at the time of performing the moderate cooling and humidifying operation, the refrigerant passage of the refrigerant cycle device is switched to a refrigerant passage of coupling the indoor condenser to the outdoor heat exchanger in parallel on the downstream side of a compressor to thereby make the outdoor heat exchanger function as a refrigerant radiator. In this case, the refrigerant radiates heat to the feed air in the indoor condenser, and the refrigerant radiates heat to the outdoor air in the outdoor heat exchanger, whereby an amount of heat absorbed by the refrigerant in the indoor evaporator can be ensured. In this way, the feed air having a low temperature can be blown off into the chamber.
In an air conditioner described in the patent document 2, at the time of performing the heating and dehumidifying operation, the refrigerant passage of the refrigerant cycle is switched to the same refrigerant passage as in the patent document 1, whereas at the time of performing the moderate cooling and dehumidifying operation, the refrigerant passage of the refrigerant cycle is switched to a refrigerant passage of coupling the indoor condenser, the outdoor heat exchanger, and the indoor evaporator in series on the downstream side of the compressor to thereby make the outdoor heat exchanger function as a refrigerant radiator. Also in this case, the refrigerant radiates heat in both of the indoor condenser and the outdoor heat exchanger, whereby an amount of heat absorbed by the refrigerant in the indoor evaporator can be ensured.
Here, in the case where the refrigerant passage of the refrigerant cycle is switched to the refrigerant passage of coupling the indoor evaporator to the outdoor heat exchanger in parallel to thereby make the outdoor heat exchanger function as the heat absorbing device, as in the case of the heating and dehumidifying operation in the patent documents 1, 2, even if an attempt to vary an amount of heat absorbed by the refrigerant in the indoor evaporator is made so as to vary the temperature of the air blown off into the chamber, the amount of heat absorbed by the refrigerant from the outdoor air in the outdoor heat exchanger cannot be adequately adjusted. As a result, the temperature adjustment range of the air blown off into the chamber is limited.
This is because in the refrigerant passage of coupling the indoor evaporator to the outdoor heat exchanger in parallel as described in the patent documents 1, 2, a refrigerant evaporation temperature in the indoor evaporator is equal to a refrigerant evaporation temperature in the outdoor heat exchanger.
For example, in order to increase the temperature of the air blown off into the chamber, it is only necessary to decrease the refrigerant evaporation temperature in the outdoor heat exchanger to thereby increase the amount of heat absorbed by the refrigerant in the outdoor heat exchanger. However, when the refrigerant evaporation temperature in the outdoor heat exchanger is decreased, the refrigerant evaporation temperature in the indoor evaporator is also decreased, so that frost can be formed on the indoor evaporator.
On the other hand, in order to decrease the temperature of the air blown off into the chamber, it is only necessary to increase the refrigerant evaporation temperature in the outdoor heat exchanger to thereby decrease the amount of heat absorbed by the refrigerant in the outdoor heat exchanger. However, when the refrigerant evaporation temperature in the outdoor heat exchanger is increased, the refrigerant evaporation temperature in the indoor evaporator is also increased, so that the feed air cannot be sufficiently dehumidified.
Further, even in the case where the refrigerant passage of the refrigerant cycle is switched to the refrigerant passage of coupling the indoor condenser to the outdoor heat exchanger in parallel as in the case of the moderate cooling and heating operation of the patent document 1, or even in the case where the refrigerant passage of the refrigerant cycle is switched to the refrigerant passage of coupling the indoor condenser to the outdoor heat exchanger in series as in the case of the moderate cooling and heating operation of the patent document 2, in the case where the outdoor heat exchanger is made to function as the refrigerant radiator, even if an attempt to increase the amount of heat radiated by the refrigerant in the indoor condenser is made in order to increase the temperature of the air blown off into the chamber, if the amount of heat radiated by the refrigerant to the outdoor air in the outdoor heat exchanger cannot be adequately decreased, to expand the temperature adjustment range of the air blown off into the chamber to a higher temperature side is limited.
In other words, in the air conditioners described in the patent documents 1, 2, at the time of performing the dehumidifying operation, the capacity (heat radiating capacity and heat absorbing capacity) of the outdoor heat exchange cannot be adequately adjusted, so that as shown in FIG. 25, there exists a range in which the temperature of the air blown off into the chamber cannot be adjusted. FIG. 25 is an illustrative drawing to illustrate a temperature adjustment range of the air blown off into a chamber in a conventional an air conditioner. In FIG. 25, R1 designates a region in which a blowoff temperature cannot be controlled, R2 designates a temperature adjustable range at the time of performing a heating and dehumidifying operation, R3 designates a region in which the blowoff temperature cannot be controlled in a middle temperature range, R4 designates a temperature adjustable range at the time of performing a moderate cooling and dehumidifying operation, and RT designates a refrigerant evaporation temperature in the indoor evaporator.
In this way, in the air conditioners described in the patent documents 1, 2, the temperature adjustment range of the air blown off into the chamber at the time of performing the dehumidifying operation can be limited in some cases, and in some cases, a comfortable air conditioning of the chamber cannot be realized.
Further, there is provided a refrigerant cycle device used for an air conditioner that cannot utilize the waste heat of an engine of an electric automobile or the like. This refrigerant cycle device is provided with: a compressor for sucking, compressing, and discharging a refrigerant; a condenser for radiating heat of the refrigerant discharged from the compressor to an external fluid; an expansion valve for reducing pressure of the refrigerant flowing out of the condenser to expand the refrigerant; and an evaporator for evaporating the refrigerant reduced in pressure by the expansion valve to thereby absorb heat from the external fluid. The evaporator and the condenser are arranged in an air-conditioning duct and the evaporator is made a heat exchanger for cooling and dehumidifying air for air conditioning and the condenser is made a heat exchanger for heating the air for air conditioning. In this way, the air-conditioned air dehumidifies and heats the interior of a vehicle compartment (patent document 3 (JP-A-2000-16072)).
However, in the refrigerant cycle device of the patent document 3, there is a case where, for example, in order to prevent frost from being formed on the evaporator for absorbing heat from the air, a lower limit is set to the pressure of the refrigerant in the evaporator. When the lower limit is set to the pressure of the refrigerant in the evaporator, a heat absorbing capacity of the evaporator is limited and hence the load of the evaporator is made low, which makes the evaporator unable to sufficiently exert its heat absorbing capacity. Hence, there is also presented a problem that an air heating capacity (capacity of heating an external fluid) of the condenser that is a refrigerant radiator will be deficient.